Oral Microbiota Display Profound Differential Metabolic Kinetics and Community Shifts upon Incubation with Sucrose, Trehalose, Kojibiose, and Xylitol

Abstract

This study compares the metabolic properties of kojibiose, trehalose, sucrose and xylitol upon incubation with representative oral bacteria as monocultures, synthetic communities or with human salivary bacteria in a defined medium. As compared to sucrose and trehalose, kojibiose resisted metabolism during a 48h incubation with monocultures, except for Actinomyces viscosus. Incubations with Lactobacillus spp. based communities, as well as salivary bacteria displayed kojibiose metabolism, yet to a lesser extent than sucrose and trehalose. Concurring with our in vitro findings, screening for carbohydrate active enzymes revealed that only Lactobacillus spp. and A. viscosus possess enzymes from glycohydrolase (GH) families GH65 and GH15 respectively that are associated with kojibiose metabolism. Donor-dependent differences in salivary microbiome composition were noted and differences in pH drop during incubation indicated different rates of sugar metabolism. Yet, functional analysis indicated lactate, acetate and formate to evenly dominate the metabolic profile for all sugars except for xylitol. 16S rRNA gene sequencing analysis and α-diversity markers revealed that significant shift of microbiome community by sugars was more pronounced in sucrose and trehalose than in kojibiose and xylitol. Streptococcus spp. a taxon linked to cariogenesis dominated in sucrose (91.8±6.4%) and trehalose (55.9±38.6%) representing a high diversity loss. In contrast, Streptococcus (5.1±3.7%) was less abundant in kojibiose which instead was dominated by Veillonella (26.8±19.6%) while for xylitol Neisseria (29.4±19.1%) was most abundant. Overall, kojibiose and xylitol incubations less stimulated cariogenic species yet closely maintained an abundance of key phyla and genera of salivary microbiome, suggesting that kojibiose has low cariogenic properties. IMPORTANCE This study provides a detailed scientific insight on the metabolism of a rare disaccharide; kojibiose whose mass production methodology has recently been made possible. While the resistance of kojibiose was established with monocultures, a delayed utilization of kojibiose was observed with communities containing lactobacilli and A. viscosus as well as with complex communities of bacteria from human saliva. Kojibiose is therefore, less metabolizable as compared to sucrose and trehalose. Moreover, although conventional sugars cause distinct shifts in salivary microbial communities, our study has revealed that kojibiose is able to closely maintain the salivary microbiome composition suggesting its low cariogenic properties. This study furthermore underscores the importance and relevance of microbial culture and ex vivo mixed cultures to study cariogenicity and substrate utilization, this is in sharp contrast with tests that solely rely on monocultures such as S. mutans, which clearly fail to capture complex interaction between oral microbiota.

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